1. Field of the Invention
The present invention relates to a method of starting operation of a fuel cell system including a fuel cell for generating electricity using a fuel gas supplied from a fuel gas supply apparatus and an oxygen-containing gas supplied from an oxygen-containing gas supply apparatus, and a DC/DC converter capable of connecting the fuel cell and an energy storage on a power feeding circuit.
2. Description of the Related Art
The fuel cell is a system for obtaining direct current electrical energy by electrochemical reactions of a fuel gas (chiefly hydrogen-containing gas) supplied to an anode and an oxygen-containing gas supplied to a cathode.
The fuel cell is promising for an application to a fuel cell vehicle, i.e., for use in a vehicle such as an automobile. For example, in a known fuel cell system (fuel cell automobile), the fuel cell and a motor driven by an inverter are directly connected, and a DC/DC converter for elevating or lowering the DC voltage is interposed between a point connecting the fuel cell and the motor, and an energy storage. The fuel cell is used as a main power source, and the energy storage is used as an auxiliary power source for assisting the main power source.
In this regard, in a fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2002-507049 (PCT), as shown in FIG. 6, an accumulator (battery) 1 is connected to a circuit network 3 through one or more DC/DC converter 2. A fuel cell (FC) 4 and auxiliary devices 5 such as a compressor are connected to the circuit network 3.
The accumulator 1 is charged in rated operation of the fuel cell 4, and energy is transmitted from the accumulator 1 to the circuit network 3 for supplying energy required for start-up operation. Operation of the DC/DC converter 2 is switched by a control device 6.
However, in Japanese Laid-Open Patent Publication No. 2002-507049 (PCT), in order to start operation of the fuel cell 4, an air pump (auxiliary device 5) is operated, and at this time, the accumulator 1 supplies energy to the circuit network 3 through the DC/DC converter 2. Therefore, energy losses occur in the DC/DC converter 2.
Further, the accumulator 1 needs to have a relatively large size for supplying sufficient energy to the air pump. Further, if any failure occurs in the DC/DC converter 2, it is not possible to start operation of the fuel cell 4.